The first thing you need to do is file a NASA report right now, not tomorrow but right now, there is a time limit but I can't remember what it is. Just remember **** happens its no big deal, all of us have filled at least one out. At the airlines it is called an FSAP and we have all filled out dozens.
The second thing you need to do is ask your flight instructor why he/she didn't tell you what a NASA report was and promptly fire him/her. You don't need to be giving that person any more of your money because they aren't teaching you.
Third let the flight school know what happened and they will be able to assist you with the NASA report. If they can't help you with the NASA report find a new flight school. Also if they don't seem to care that their flight instructor had a pilot deviation and didn't report it, then find a new flight school they do not deserve anymore of your money.
Fourth sleep well you are not in trouble unless you DON'T file a NASA report.
Fifth Im not joking if your flight instructor seriously did not tell you about a NASA report, help you fill one out, and did not fill one out themselves then you need a new flight instructor.